Yamagata H, Kunimatsu K, Kamasaka H, Kuramoto T, Iwasaki T
Laboratory of Biochemistry, Faculty of Agriculture, Kobe University, Japan.
Biosci Biotechnol Biochem. 1998 May;62(5):978-85. doi: 10.1271/bbb.62.978.
A bifunctional alpha-amylase/subtilisin inhibitor (RASI) was purified to electrophoretic homogeneity from rice (Oryza sativa L.) bran. Its molecular mass was 21 kDa by SDS-PAGE and its isoelectric point was 9.05. Purified RASI inhibited subtilisin Carlsberg strongly and inhibited alpha-amylase from germinating rice seeds weakly. It inhibited rice alpha-amylase more than barley alpha-amylase, and the inhibition of rice alpha-amylase was greater at higher pHs. RASI did not inhibit trypsin, chymotrypsin, cucumisin, or mammalian alpha-amylase. The RASI was in the outermost part of the rice grain and its subcellular site seemed to be aleurone particles in aleurone cells. SDS-PAGE and western blotting showed that RASI was synthesized in the late milky stage in developing seeds, and it remained fairly constant during the first 7 days of germination.
从水稻（Oryza sativa L.）麸皮中纯化出一种双功能α-淀粉酶/枯草杆菌蛋白酶抑制剂（RASI），达到电泳纯。通过SDS-PAGE测定其分子量为21 kDa，等电点为9.05。纯化的RASI对枯草杆菌蛋白酶卡尔伯格有强烈抑制作用，对发芽水稻种子的α-淀粉酶有较弱抑制作用。它对水稻α-淀粉酶的抑制作用比对大麦α-淀粉酶的抑制作用更强，且在较高pH值下对水稻α-淀粉酶的抑制作用更大。RASI不抑制胰蛋白酶、胰凝乳蛋白酶、黄瓜蛋白酶或哺乳动物α-淀粉酶。RASI位于水稻籽粒的最外层，其亚细胞定位似乎是糊粉层细胞中的糊粉粒。SDS-PAGE和蛋白质免疫印迹表明，RASI在发育种子的乳熟后期合成，在萌发的前7天保持相对稳定。
